Before remelting scrap glass, organic binders and sizes on the surface of the glass must be removed. If this is not done, the glass will enclose the remaining binder in the form of carbon. Upon remelting, carbon will reduce the glass. This reduced darkened glass is undesirable for both glass composition and melting.
One method of doing this is to mill the scrap glass and blend it with granular raw batch before charging the batch to the furnace. It is important to ensure that oxidizing conditions are maintained in the glass melt within the furnace so that the glass furnace may feed a fiberizing process without harmful effects.
This process has many inherent disadvantages. For example, the scrap glass must be passed through a shredding operation and stored in a silo before blending with conventional granular batch. Further, the process demands that an entire glass furnace be kept at oxidizing conditions to ensure that carbonaceous material is removed.
Still another process for reusing scrap glass includes the steps of removing binders or sizes from the scrap glass, remelting the scrap glass and feeding the molten scrap directly into a furnace. Binder removal and melting of the scrap glass are carried out in a separate scrap remelt furnace.
This process also has many inherent disadvantages. Additional energy is required to pyrolize the organic binder and melt the scrap in the separate remelt furnace. Special heated platinum handling equipment is needed to transfer the molten scrap to a glass melting furnace.